8/9/2019 The History and Philosophy of Astronomy Lecture 6: Middle Ages. Islam. Presentation

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The History and Philosophyof Astronomy

(Lecture 6: Middle Ages/Islam I)

Instructor: Volker BrommTA: Jarrett Johnson

The University of Texas at Austin

Astronomy 350L

(Fall 2006)

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Medieval Astronomy and Cosmology

Middle Ages/Islam I (Sep. 19)

- Decline of Western (Mediterranean) Civilization- Early Middle Ages (Dark Ages): 500 1000 AD- Ascendancy of Islamic Astronomy (800 1400 AD)

- Preservation and transformation of ancient knowledge

Middle Ages/Islam II (Sep. 21)

- Recovery of European Civilization

- High and Late Middle Ages (c. 1000 1450 AD)- Setting the Stage for the Copernican Revolution

- Recasting of the Ancient Tradition

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The Fall of Rome

Barbarians (Germanic tribes/Huns) at the gate

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The Fall of Rome

Barbarians (Germanic tribes/Huns) at the gate

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The Fall of Rome

Q: Why did it happen?

(Edward Gibbon, 1737-94)

Gibbons Decline and Fall of theRoman Empire:-decadent society

- economical pressure- constant threat of invasion- corrupt government

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The European Dark Ages

Early Christianity initially hostile towardpagan learning, especially astronomy/astrology

Loss of libraries and ancient texts

Greek language was largely forgottenonly simplified Latin

Life was brutish and short, primitive economic level

a tremendous decline in cultural sophistication

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A Rescue Attempt: Boethius (480-524 AD)

The Last Roman

Court official underTheoderic, King of theOstrogoths (ruler of

post-Roman Italy)

executed for treason

The Consolation of Philosophy

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A Rescue Attempt: Boethius (480-524 AD)

His (hyper-ambitious) program:

AristotlePlato

Greek Latintranslate

Logical works

ran out of time: most texts lost for Latin West!

only rescued Plato text: Timaeus (trans. Calcidius)

(Greek) works of astronomy forgotten for centuries!

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Kosmas Indikopleustes (6th cent. AD)

Repudiating the idea that Earth is a Sphere!

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Kosmas Indikopleustes (6th cent. AD)

Very low standard of secular learning!

Re-accept spherical Earth only 500 years later!

Universe is tabernacle!

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The Ascendancy of Medieval Islam

Emergence of vibrant and tolerant civilization!

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Islam: The Need for Astronomy

religious requirements:

- predict beginning of month

- altitude of Sun (hours of prayer)

establish office of muwaqqit

(mosque timekeeper)

Astronomers respectedposition in society!

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The House of Wisdom in Baghdad (9th cent. AD)

Vigorous effort to translate Greek texts into Arabic- Caliph al-Mamun (Abbasid dynasty, 750 1258)

Translating Ptolemy:

Greek: Syntaxis Arabic: Almagest

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Ptolemaic System within Islamic Astronomy

Almagest

No fundamental modification

to Aristotelian-Ptolemaic cosmology!

Improvements in precision- building of major observatories!

- improved mathematical methods!

Discussion of doubts about Ptolemy!

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Precision Astronomy: Great Observatories

Ulugh Beg (d. 1449) Samarkand

- Grandson of Tamerlane - Great mural sextant

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Ulugh Begs Star Catalogue

first major new catalogueof stars since time of

Hipparchus (2nd

cent. BC)

high-precision (> 1000 stars)

unknown in Europe

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The Astrolabe: Universal Astro-calculator

invented by Greeks, butperfected by Arabs

measure altitude (height)

of stars (or Sun)

predict position ofstars/Sun at given time

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Critiquing Ptolemy

Averroes (1126-98 AD)

lived in Moorish Andalusia

The Commentatorof Aristotle

philosophical purist:

found contrived modelof Ptolemy (deviation from

uniform spherical motion)inelegant

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Critiquing Ptolemy

Nasir al-Din al-Tusi (1201-74 AD)

lived in Persia

adviser to Mongolconqueror Hulagu Khan

one of greatest astronomers

during Islamic Period

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Al-Tusis Observatory at Maragha

12 years of intense effort: Planetary Tables (zij)

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Al-Tusis Attack on Ptolemy

Copernicus did the same: Did he know of al-Tusi?

eliminate un-Platonic equant with double epicycle!equant double-epicycle

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Legacy of Islamic Astronomy

Preserved ancient Greek astronomy / philosophy

Improved mathematical methods

Diligent observers (astronomical tables)

Attitude towards Ptolemaic Framework:

- no fundamental change!- improved precision (Great Observatories)- raising of doubts- elimination of Ptolemaic equant